Electrostatic discharge testing is the process of testing a device’s resistance to electrostatic discharge, or ESD. ESD occurs when two electrically charged objects contact each other, are involved in an electrical short or suffer a dielectric breakdown, resulting in a sudden flow of electricity. This often creates a visible spark, or discharge. Electrostatic discharges damage sensitive electronic equipment, causing equipment to fail and networks to go down, and can potentially trigger explosions in gas, coal dust or fuel vapor. Test engineers perform ESD testing to guarantee that their products achieve immunity to these discharges, whether they are introduced to currents from the human body, machines or charged devices.
ESD Test Equipment
ESD guns, also known as ESD simulators, are handheld tools used to test the immunity of products to electrostatic discharge. An ESD gun is generally programmable, allowing users to test with a discharge voltage of up to 16 kV or 30 kV, and capable of fulfilling EMC standards like IEC/EN 61000-4-2. Different standards can be achieved in accordance with different RC networks with different rise times and pulse widths.
Popular models consist of the following:
ESD Test Procedures
ESD immunity testing simulates discharges on devices with high frequency ESD pulses generated by ESD guns, either through direct contact with the equipment under test or air-gap discharge as described by IEC 61000-4-2. ESD test methods account for the most common real-life instances of ESD and are divided into the following models.
- Human Body Model (HBM)
- The Human Body Model is the most common ESD test and applies to electronic components designed for personal use. An HBM test simulates cases in which a charge accumulates on the human body and results in electrostatic discharge, which occurs when humans build up residual charge from mundane activities like dragging their feet on the floor.
- Machine Model (MM)
- The Machine Model is performed on electronic components developed for manufactured devices. MM ESD tests consist of mimicking a charge which, when accumulated on metal equipment or tools, causes ESD. A machine in industrial-automation manufacturing, for example, may carry an electrical charge, and upon contact with a component, trigger electrostatic discharge.
- Charged Device Model (CDM)
- The Charged Device Model is also for the electronic components of manufactured devices. The CDM replicates cases in which a charge accumulates on the DUT, causing ESD; this often occurs in environments with machines that are always on.
Watch the following video for an overview of ESD test models.
ESD Test Standards
ESD tests are a part of EMC testing—the measurement of a device or system’s electromagnetic compatibility. Specifically, ESD falls under the conducted susceptibility (CS) category. EMC is demonstrated by achieving compliance to test requirements developed by internationally recognized standards like MIL-STD-461G CS and IEC 61000-4. Complying to standards is key to ensuring your device is immune to electromagnetic interference (EMI) and ready for the market. The most recognized identification of conformity with health, safety and environmental protection standards for products sold within the European Economic Area (EEA) is CE marking. The following standards can help you reach CE marking for your product(s).
Common ESD Test Standards